One of the flaws of sorcerers is that their magic is inborn. Of course, there's nothing wrong with that. The problem is the bad way this is implemented. Sorcerers' magic is inborn, and they haven't chosen to be sorcerers. Yet, they strangely get to choose which spell they can cast. On the other hand, the new spells they learn each level are earned through practice, and it seems natural for them to choose these. So this is what we do to sorcerers:

Choose the spells they know at first level randomly.

We'll come back to this later.

There's another problem that arises from the fact that sorcerer magic is inborn. When you are a sorcerer, you have inborn magic potency, and you have realized it. Even if the class you choose at first level isn't sorcerer, you can still multiclass into sorcerer later, you just realize your magic potetial the moment you multiclass sorcerer. However, this means that actually ALL PC's have magic potential. Because if some don't have, they wouldn't be able to multiclass sorcerer, and everybody can.
In addition, all sorcerers are born with their potential, but a player character isn't born at character creation. The player merely "picks him up" at that point. But what if the player early as a child discovers the sorcerous powers, fiddles around with, say, one spell a day, but then leaves it at that and goes to monk school?

So, to fix these two problems we do two things:

You can't multiclass into sorcerer. If you don't have it as your first class, you can never get it.

Create the following feat:

Inborn Arcana

You have a sorcerous potential.

Prequisites: Must be taken at first level. You can't be a sorcerer when you take this feat.

Benefits: You either know a single first-level spell and can cast it once per day, or three 0th-level spells and can cast them a total of three times per day. This is spontaneous casting, and the spell(s) are chosen randomly. In addition, it's possible for you to multiclass into sorcerer.

Sorcerers can't specialize, and goddamnit, that's annoying! It's totally impossible for a sorcerer to be born with more power for, say, evocation, than other schools of magic. Of course, with the basic sorcerer rules, you can just choose to know only evocation spells. but this doesn't make you any more powerful at evocation, it just mean that you know more different evocation spells.

And you can't even do that if you take my first rule change into account. To achieve a focused sorcerer, but not make it a clone of wizard specialication, this is what i do:

Make it possible for sorcerers to choose a specialication school

Make all spells from that school count as one spell slot lower.

A specialized sorcerer must choose THREE prohibited schools.

The sorcerer's random starting spells will all be from his specialized school.

Important Note: This section hasn't been tested. It may very well be very unbalanced. I'd be very happy if somebody who is using my variant rules would edit this section after their own experiences. Specifically, the number of prohibited schools could probably be better.

Sorcerers may gain their power in many ways, but its often in their blood. While it's fine to not ever think about it, here's a few feats to distinguish between different sources of sorcerous power. If you havent got any of these feats, you just haven't discovered where your power comes from yet:

Celestial Blood

You have realized that your sorcerous powers come from celestial blood.Prerequisites: Must be a sorcerer. Must be good aligned.Benefit: spell with the good descriptor (including ones cast to summon good creatures) are cast at +1 caster level

Fiendish BloodYou have realized that your sorcerous powers come from fiendish blood.Prerequisites: Must be a sorcerer. Must be evil aligned.Benefit: spell with the evil descriptor (including ones cast to summon evil creatures) are cast at +1 caster level

Draconic BloodYou have realized that your sorcerous powers come from draconic blood.Prerequisites: Must be a sorcerer.Benefit: choose a dragon type from the table below. you gain the benefits stated for that dragon type.